M12 Nut Dimensions: Hex & Thin Series

Q: What size wrench or spanner do I need for an M12 nut?

An M12 hex nut typically requires a 19 mm wrench or socket (according to ISO 4032). However, many standard M12 nuts following the older DIN 934 standard utilize an 18 mm wrench. It is recommended to check your specific fastener standard before selecting a tool.

Q: What is a jam nut?

A jam nut is a low-profile hex nut, typically from the Thin Series (DIN 439), that is used to lock a standard nut in place. By tightening a standard nut against a jam nut, you create internal tension between the threads of both nuts and the bolt. This “jams” the assembly together, providing a mechanical lock that prevents loosening caused by vibration or rotation.

Q: Can a Thin Series nut handle the same torque as a Regular nut?

No. Because the Thin Series has fewer threads in contact with the bolt, it has a lower proof load. Applying the high torque levels required for a structural M12 joint will likely strip the threads of a thin nut. For primary load-bearing connections, always use a Regular Series nut.

M12 nut dimensions or sizes are critical for structural steelwork, automotive suspension systems, and heavy industrial equipment. This size is specifically engineered to mate with fasteners having a 12.00 mm nominal diameter and is available in M12 x 1.75 for the coarse series and M12 x 1.25 for the fine series.

This charts covers both the Regular Series (DIN 934 / ISO 4032) for standard load-bearing applications and the Thin or Half Series (DIN 439 / ISO 4035), which is ideal for jam nut or lock nut configurations or applications with limited vertical clearance. The thread dimensions comply with DIN 13-1 (coarse), DIN 13-21 (fine series), and ISO 68-1 standards to ensure a precise fit and reliable engagement across high-stress metric fastening systems.

Disclaimer: Actual dimensions, including the width across flats (spanner or wrench size), nut height, and thread tolerance may vary depending on the specific manufacturing class and material — always verify with the official product datasheet before use or buying.

Nut internal thread diagram depicting major diameter, minor diameter, and pitch diameter

Nut body diagram depicting width across flats, width across corners, diameter, and thickness or height

M12 x 1.75 Hex Nut – DIN 13-1/ISO 68-1
Dimension	Size (mm)
Dimension	Min	Max
Major Diameter	12	12.453
Pitch Diameter	10.863	11.063
Minor Diameter	10.106	10.441
Thread Pitch	1.75

M12 x 1.5 Hex Nut – DIN 13-21/ISO 68-1
Dimension	Size (mm)
Dimension	Min	Max
Major Diameter	12	12.406
Pitch Diameter	11.026	11.216
Minor Diameter	10.376	10.676
Thread Pitch	1.5

M12 x 1.25 Hex Nut – DIN 13-21/ISO 68-1
Dimension	Size (mm)
Dimension	Min	Max
Major Diameter	12	12.36
Pitch Diameter	11.188	11.368
Minor Diameter	10.647	10.912
Thread Pitch	1.25

M12 x 1.0 Hex Nut – DIN 13-21/ISO 68-1
Dimension	Size (mm)
Dimension	Min	Max
Major Diameter	12	12.304
Pitch Diameter	11.35	11.51
Minor Diameter	10.917	11.153
Thread Pitch	1.0

M12 Hex Nut – DIN 934/ISO 4032 & ISO 8673
Diameter	12	13
Width Across Flats	17.73	18
Width Across Corners	20.03	Not specified
Height / Thickness	10.37	10.8

M12 Thin / Half Nut – DIN 439/ISO 4035 & ISO 8675
Diameter	12	13
Width Across Flats	18.67	19
Width Across Corners	21.1	Not specified
Height / Thickness	5.7	6

Metric to Inch Converter

Enter mm to convert to inches

Previous & Next Size Chart
← M10
→ M14

← Choose Another Size

Frequently Asked Questions

What size wrench or spanner do I need for an M12 nut?

An M12 hex nut typically requires a 19 mm wrench or socket (according to ISO 4032). However, many standard M12 nuts following the older DIN 934 standard utilize an 18 mm wrench. It is recommended to check your specific fastener standard before selecting a tool.

What is a jam nut?

A jam nut is a low-profile hex nut, typically from the Thin Series (DIN 439), that is used to lock a standard nut in place. By tightening a standard nut against a jam nut, you create internal tension between the threads of both nuts and the bolt. This “jams” the assembly together, providing a mechanical lock that prevents loosening caused by vibration or rotation.

Can a Thin Series nut handle the same torque as a Regular nut?

No. Because the Thin Series has fewer threads in contact with the bolt, it has a lower proof load. Applying the high torque levels required for a structural M12 joint will likely strip the threads of a thin nut. For primary load-bearing connections, always use a Regular Series nut.